1. Field of the Invention
The present invention relates to cationic surfactants based on quanternary ammonium compounds and their use in cleaning solutions. More specifically, the present invention relates to quaternary ammonium cationic surfactants having corresponding anions with anticorrosive properties.
2. Description of Related Art
Industrial processes for cleaning unfinished and/or finished products, for example automotive parts made of iron or steel, use aqueous solutions containing tensides and other materials such as builders, complexing agents, organic and/or inorganic anticorrosive agents and others. Thus, U.S. Pat. No. 4,284,434 and German Published Appln. No. 32 47 431 propose using quaternary ammonium compounds, in the alkaline pH range, as cationic surfactants together with cleaning components in which alkyl residues of varying chain lengths are bonded to the ammonium nitrogen atom. The corresponding anions of these quaternary ammonium cations are typically chloride, sulfate and methylsulfate anions which are known to promote corrosion, especially the corrosion of equipment parts and the treated metal products themselves. This is extremely disadvantageous, especially in processes treating metal surfaces with aqueous products, and particularly in cases where higher concentrations of cationics are desired. The corrosive tendencies of these solutions cause problems not only during long term storage of the treated parts, but also immediately after they are treated.
U.S. Pat. No. 4,443,363 discloses tenside mixtures used to clean bottles and other articles having hard surfaces (porcelain, synthetics, metal). These mixtures contain cationic tensides based on ammonium compounds. Unfortunately, these tensides also contain corrosive chloride, bromide and/or methylsulfate anions. These anions also tend to corrode the equipment used to apply the surfactant solutions (e.g., dish washers).
German Published Application No. 33 21 608 discloses processes for preparing quaternary ammonium compounds containing at least one long-chain hydroxyalkyl residue. The compounds are prepared by reacting the salt of a tertiary amine and an organic acid in water with a terminal epoxide compound and introducing a hydroxyalkyl residue at standard pressure, at a temperature between 40.degree. C. and 100.degree. C. and at a pH of at least 7. However, the resulting quaternary ammonium compounds, also fail to meet the high requirements set for commercial cationic surfactants with respect to practical serviceability and anticorrosive properties.
Anions of many organic acids are unsuitable as the corresponding anions of cationic surfactants, since the resulting quaternary ammonium compounds have poor solubility in water. These compounds generally have a paste-like consistency and, due to their poor solubility in water, cannot be used in making industrial cleaners. In addition, ammonium cations containing numerous hydroxyalkyl groups cause undesirable precipitations in water which has not been fully de-salted. This renders the use of such cations impractical.
Cationic surfactants are often expected to exhibit de-emulsifying and/or defoaming action on emulsions and/or anionic surfactants or emulsifiers, respectively. However, the quaternary ammonium compounds disclosed in German patent application No. 33 21 608.8 show n de-emulsifying action on emulsions and/or anionic emulsifiers. Furthermore, the lack of de-emulsifying and/or defoaming properties have not been compensated by any improved anticorrosive properties in these surfactants.